Sizing apparatus for cardiac prostheses and method of using same

ABSTRACT

A sizing apparatus and a method for ascertaining a size for a cardiac prosthesis are disclosed. Specifically, the sizing is implemented by positioning a contact member at a patient&#39;s heart valve for engagement by one or more viable leaflets of the patient&#39;s valve. The size is determined based on the engagement between the contact member and the leaflet (or leaflets) of the patient&#39;s valve.

TECHNICAL FIELD

[0001] The present invention relates generally to cardiac prosthesesand, more particularly, to a sizing apparatus for a cardiac prosthesisand method of using the apparatus.

BACKGROUND

[0002] A heart valve can become defective or damaged, such as resultingfrom congenital malformation, disease, or aging. When the valve becomesdefective or damaged, the leaflets may not function properly. One commonproblem associated with a degenerating heart valve is an enlargement ofthe valve annulus (e.g., dilation). Other problems that may result invalve dysfunction are chordal elongation and lesions developing on oneor more of the leaflets.

[0003] The bicuspid or mitral valve is located in the leftatrioventricular opening of the heart for passing blood unidirectionallyfrom the left atrium to the left ventricle of the heart. The mitralvalve is encircled by a dense fibrous annular ring and includes twovalve leaflets of unequal size. A larger valve leaflet, which is knownas the anterior leaflet, is located adjacent the aortic opening. Thesmaller leaflet is the posterior leaflet.

[0004] When a mitral valve functions properly, for example, it preventsregurgitation of blood from the ventricle into the atrium when theventricle contracts. In order to withstand the substantial backpressureand prevent regurgitation of blood into the atrium during theventricular contraction, the cusps are held in place by fibrous cords(cordae tendinae) that anchor the valve cusps to the muscular wall ofthe heart.

[0005] By way of example, if an annulus enlarges or dilates to a pointwhere the attached leaflets are unable to fully close (malcoaptation),regurgitation or valve prolapse might occur. Adverse clinical symptoms,such as chest pain, cardiac arrhythmias, dyspnea, may manifest inresponse to valve prolapse or regurgitation. As a result, surgicalcorrection, either by valve repair procedures or by valve replacement,may be required.

[0006] Surgical reconstruction or repair procedures may includeplication, chordal shortening, or chordal replacement. Another commonrepair procedure relates to remodeling of the valve annulus (e.g.,annuloplasty), which may be accomplished by implantation of a prostheticring to help stabilize the annulus and to correct or help preventvalvular insufficiency which may result from defect or dysfunction ofthe valve annulus. Properly sizing and implanting the annuloplasty ringcan substantially restore the valve annulus restored to its normal,undilated, circumference. In situations where the valve leaflets exhibitlesions, it also may be necessary to reconstruct one or more valveleaflets by securing grafts or patches to the leaflets, such as overlesions or holes formed in the leaflet. The repair or reconstruction ofthe leaflets may be complicated and time consuming, the results of whichare not readily reproducible.

SUMMARY

[0007] The following presents a simplified summary of the invention inorder to provide a basic understanding of some aspects of the invention.This summary is not an extensive overview of the invention. It isintended to neither identify key or critical elements of the inventionnor delineate the scope of the invention. Its sole purpose is to presentsome concepts of the invention in a simplified form as a prelude to themore detailed description that is presented later.

[0008] The present invention relates generally to a sizing apparatus fora prosthetic device intended for implantation at a heart valve toimprove operation of a defective or damaged valve. The apparatusincludes a contact member having a curved surface that is configured tobe engaged by one or more functioning leaflets of a heart valve within apatient when the contact member is positioned at the heart valve. A usercan observe engagement between the functioning leaflet and the contactmember to determine an appropriate size of cardiac prosthesis. Theobservations, for example, can be made under direct vision (e.g., duringan open chest procedure) or via an appropriate vision system (e.g.,during an open or closed chest procedure). Additionally, where thecurved surface is not of an appropriate size, the cross-sectionaldimension of the contact member can be changed, such as by eitheremploying a different contact member or by using a contact member inwhich the size of the curved surface is adjustable, until an appropriatesize is can be determined. Alternatively, a user may be able to gauge anappropriate size based on observed a sizing discrepancy between theleaflet and the contact member. An appropriately sized prosthetic devicecan then be implanted based on the sizing.

[0009] In accordance with another aspect of the invention, a sizingapparatus for a prosthetic device includes a contact member and anelongated member extending from the contact member and terminating in aproximal end. The contact member includes a curved surface that isconfigured to be engaged by at least one functioning leaflet of a heartvalve within a patient when the contact member is positioned at theheart valve. The elongated member includes an aperture extending throughfrom a proximal end of the elongated member and terminating in anopening proximal the contact member. The aperture facilitates the flowof fluid through the contact member into a chamber of the heart to urgethe functioning leaflet toward the contact member.

[0010] In accordance with yet another aspect of the invention, a sizingapparatus for a prosthetic device includes a contact member and anelongated member extending from the contact member and terminating in aproximal end. The contact member includes a curved surface that isconfigured to be engaged by at least one functioning leaflet of a heartvalve within a patient when the contact member is positioned at theheart valve. The contact surface is configured to have a variablecross-sectional dimension. The contact surface can assume at least areduced cross-sectional dimension to facilitate positioning of thecontact member at the heart valve. The contact surface can beselectively expanded to an expanded cross sectional dimension, such thatthe at least one leaflet can engage the contact member to facilitatedetermining the size of a desired cardiac prosthesis.

[0011] To the accomplishment of the foregoing and related ends, theinvention, then, comprises the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative aspects ofthe invention. These aspects are indicative, however, of but a few ofthe various ways in which the principles of the invention may beemployed. Other objects, advantages and novel features of the inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is an elevated side view of an example apparatus inaccordance with an aspect of the present invention.

[0013]FIG. 2 is a cross-sectional view of the taken along line 2-2 ofFIG. 1.

[0014]FIG. 3 is a view of the apparatus taken along line 3-3 of FIG. 2.

[0015]FIG. 4 is a cross-sectional view of the apparatus positionedwithin the heart valve of a patient, illustrating a first condition ofthe heart valve.

[0016]FIG. 5 is an overhead (inflow) view of the apparatus positionedwithin the heart valve of a patient, illustrating a first condition ofthe heart valve.

[0017]FIG. 6 is a cross-sectional view of the apparatus positionedwithin the heart valve of a patient, similar to FIG. 4, illustrating asecond condition of the heart valve.

[0018]FIG. 7 is an overhead (inflow) view of the heart valve and theapparatus, similar to FIG. 5, illustrating a second condition of theheart valve.

[0019]FIG. 8 is an assembly view of an apparatus in accordance with anaspect of the present invention with a contact member detached from theelongated member.

[0020]FIG. 9 is an example of a contact member in accordance with anaspect of the present invention.

[0021]FIG. 10 is another example of a contact member in accordance withan aspect of the present invention.

[0022]FIG. 11 is an isometric view of a cardiac prosthesis that can beemployed in accordance with an aspect of the present invention.

[0023]FIG. 12 is a cross-sectional view of a part of a heart in whichthe cardiac prosthesis is implanted at a heart valve in accordance withan aspect of the present invention.

[0024]FIG. 13 is an elevated side view of a sizing apparatus inaccordance with another aspect of the present invention.

[0025]FIG. 14 is an overhead view of a sizing apparatus in accordancewith yet another aspect of the present invention.

DESCRIPTION

[0026] The present invention relates generally to a sizing apparatus fora cardiac prosthesis. The sizing apparatus can be used to determine theappropriate size for a cardiac prosthesis (e.g., a valvuloplasty device)that can be implanted into the heart valve to cooperate with at leastone of the leaflets of the patient's own valve, which can be thepatient's native valve or a previously implanted prosthesis.Specifically, the sizing tool of the present invention includes acontact member that can be engaged by one or more viable leaflets of apatient's heart valve to ascertain the proper size for a cardiacprosthesis.

[0027]FIGS. 1-3 illustrate a sizing apparatus 10 in accordance with oneaspect of the invention. The apparatus 10 includes a contact member 12.The contact member 12 has a curved surface 14 configured to be engagedby a leaflet within a heart valve. For example, the curved surface 14can be configured to engage the anterior leaflet of the mitral valve ofa patient's heart.

[0028] In accordance with the present aspect of the invention, thecontact member 12 can be fabricated from any substantially rigid,durable material that is substantially biocompatible. By substantiallyrigid, it is meant that the contact member 12 should be capable ofholding its basic shape under a moderate amount of pressure. By durable,it is meant that the device should be able to withstand standardsterilization techniques, such as by an autoclave or other sterilizer.Example materials that can be used for the contact member includedurable plastics (e.g., formed of DELRIN®) and non-reactive metals, suchas surgical steel. Those skilled in the art will understand andappreciate other types of materials that also could be employed to formthe contact member, all of which are contemplated as falling within thescope of the present invention.

[0029] An elongated member 16 extends from the contact member 12 toterminate in a proximal end 20 that is spaced apart from the contactmember. In the example of FIGS. 1-3, the elongated member is depicted asa generally cylindrical, elongated rod or tube, which can be hollow. Asshown in FIG. 2, an aperture 22 extends through the elongated member 16from its proximal end 20 to an opening located near a surface 18 of thecontact member 12 opposite the surface 14.

[0030] The elongated member 16 can be formed of a durable and generallyrigid material. The elongated member 16 can be formed of the same or adifferent material than the contact member 12. The length andcomposition of the elongated member 16 can vary, depending on theapplication. For example, some applications can require a lengthyelongated member 16 or an elongated member formed form a more flexiblematerial. Those skilled in the art will appreciate that differentmaterials and lengths can be selected depending on the design of thedevice and the desired application.

[0031] The elongated member 16 can also be formed of multiple portions,which can be the same or different materials. For example, the elongatedmember illustrated in FIG. 2 begins at its proximal end 20 as a plasticmaterial. The inside of that portion of elongated member can be threaded(or otherwise configured) to accept a spout 24, which can be made fromstainless steel (or any other generally rigid material) that terminatesnear the contact member 12. Alternatively, the contact member 12 can beformed from a single material, such as a metal or plastic material.

[0032] The contact member 12 is dimensioned to a size consistent withthat of a leaflet within a heart valve. For example, a contact member 12approximating the size of a leaflet within an adult human mitral valvecan have a width (indicated at W in FIG. 3) ranging from fifteen tofifty millimeters. Those skilled in the art will appreciate that thewidth of the contact member can vary according to the application. Forexample, in a heart valve sizing apparatus intended for use in childrenor small animals, a width smaller than fifteen millimeters may beappropriate. An apparatus intended for use in large animals, such ashorses, might require a contact member with a width greater than fiftymillimeters.

[0033] As shown in FIG. 2, a longitudinal axis 26 extends longitudinallythrough the elongated member 16 substantially parallel to the aperture22. While the member 16 is depicted as being substantially straight, itwill be appreciated that it alternatively could be curved or formed aflexible material to facilitate curving the member. The contact surface14 is curved in a convex manner relative to the axis 26. Another axis28, shown in FIG. 3, is substantially perpendicular to the axis 26 andcoincides with the longest dimension (e.g., the width W) of the contactmember 12. The contact surface 14 is curved relative to the horizontalaxis 28 in a concave manner (e.g., curves away). As a result of thiscurvature, the contact member 12 is configured to approximate a leafletof a heart valve at closure of the valve.

[0034] The proximal end 20 of the elongated member 16 can connect to asleeve-like conduit interface 30, as depicted in FIG. 1. The conduitinterface 30 can be made from any durable, flexible material that issubstantially biocompatible. Example materials include rubber orsilicon, although other types of materials can also be used. Theproximal end 32 of the conduit interface 30 is adapted to connect to afluid source 34, which can include a syringe or other type of devicecapable of injecting fluid through the aperture 22. This adaptationallows the conduit interface 30 to fit tightly over a nozzle 36 of thefluid source 34, while the other end 37 of the conduit interfaceconnects to the proximal end 20 of the elongated member 16. The conduitinterface 30 thus can interconnect the elongated member 16 and thenozzle 36 to provide a substantially fluid-tight seal to enable the flowof fluids therethrough.

[0035] The fluid source 34 contains a quantity of a fluid that can bepassed through the aperture 22 of the elongated member 16. A number offluids can be used, including air, water, saline, and blood to name afew. In the illustrated apparatus, the fluid source includes a syringe38. The syringe 38 can be used to expel fluid from the fluid source 34through the nozzle 36 and into the aperture 22 of the elongated member16. One skilled the art will perceive other devices for controlling theflow of fluid from the fluid source, such as stop cocks and mechanicalor electric pumps, and the use of these devices is intended to beencompassed within the claimed invention. The fluid source 34 can beformed from a number of materials. For example, transparent materials,such as clear plastics and glass, can be used, as they allow a user todetermine more easily the fluid level within the fluid source 34.

[0036] In view of various structural features of a sizing apparatus, inaccordance with an aspect of the invention, use of such an apparatus tofacilitate implantation of cardiac prosthesis will be better appreciatedwith reference to FIGS. 4-12. For example, as illustrated in FIGS. 4-7,implantation of a prosthesis can include the use of a sizing tool 52 toascertain an appropriate size for a prosthetic device in accordance withan aspect of the present invention.

[0037] In FIG. 4, the sizing tool 52 has been inserted into a heartvalve 54. Solely for the purpose of example, the valve 54 is illustratedin FIGS. 4-12 as a mitral valve within a human heart, and the method isdiscussed in the context of implanting a prosthesis to replace theposterior leaflet within the mitral valve. One skilled in the art willappreciate, however, that the apparatus of the present invention may beused in other valves within the human heart, such as the tricuspid,pulmonary, or aortic valves, as well as in valves within animal hearts.Likewise, the present invention may be used to size a replacement forany leaflet, including the anterior leaflet of the mitral valve or theleaflets of any of the aforementioned valves. Such uses are intended tobe encompassed in the appended claims.

[0038] The chamber above the mitral valve 54 is the left atrium 56 andthe chamber below the valve is the left ventricle 58. In FIG. 4, theanterior leaflet 60 is present and viable, but the posterior leaflet(not shown) is either nonviable or has been removed. A contact member 62of the sizing tool 52 is positioned at the position formerly occupied bythe posterior leaflet, with a contact surface 64 facing the anteriorleaflet 60. In accordance with one aspect of the present invention, thecontact member 62 can be positioned manually by a user holding anelongated handle 66 or other structure attached to the member. An inflowview of the open valve 54 and sizing apparatus 52 is shown in FIG. 5.

[0039] The user would employ a fluid source 68 in fluid communicationwith the apparatus 52 to supply fluid into the ventricle 58. Such fluidthus flows through an aperture 70 within the elongated handle 66 intothe left ventricle 58. As discussed previously, this can be accomplishedby a number of methods, such as a pump, syringe, or a stopcock. As theleft ventricle fills 58 with fluid, the anterior leaflet 60 is urgedtoward its closed position and toward the contact member 62. Dependingon whether the apparatus 52 is an appropriate size, the anterior leaflet60 can engage with the contact member 62 to close the valve, asillustrated in FIG. 6.

[0040] Once the anterior leaflet 60 has been urged into a closedposition, the surgeon can examine the engagement between the anteriorleaflet and the contact member 62. Where the leaflet 60 and the contactmember 62 coapt, as to substantially prevent the flow of fluid throughfrom the valve, a size of a corresponding prosthesis can be determinedaccording to the size of the contact member 62. An inflow view of aleaflet 60 coapting with a contact member 62 is illustrated in FIG. 7.When the leaflet 60 and the contact member 62 coapt properly, thesurgeon will know that a prosthetic device matching the size and shapeof the contact member 62 is appropriate for a prosthetic replacement.Where there is not sufficient coaptation between the leaflet 60 and thecontact member 62, a differently sized prosthesis should be used.

[0041] For example, where the contact member 62 is too small toeffectively coapt the leaflet 60, the surgeon may see small spaces orgaps between the leaflet and the contact member. This indicates a largersize prosthesis may be needed. This can be confirmed by repeating thesizing process with a larger sized contact member.

[0042] Where the contact member 62 is too large, the annulus of thevalve 54 may distort, thereby preventing desired coaptation between thecontact member 62 and the leaflet. Additionally or alternatively, theorifice between the contact member 62 and the leaflet may be consideredbe too small. A surgeon thus can readily ascertain that a prostheticdevice matching the size of the contact member would be too large andseek a smaller device.

[0043]FIG. 8 illustrates an apparatus 80 is provided where a contactmember 82 can be made selectively detachable from an elongated member 84In accordance with an aspect of the present invention. The selectiveattachment allows a surgeon to select from a number of alternate contactmembers of different size if the original contact member 82 is too largeor too small. By way of example, the distal end of the elongated member84 can be threaded to allow a contact member to be screwed onto theelongated member. Those skilled in the art will appreciate other typesof connections or fittings (e.g., friction fitting, snap fitting, andthe like).

[0044]FIGS. 9 and 10 illustrate examples of alternative contact members,86 and 88. With the new contact member, the surgeon can repeat thesizing procedure described above to better approximate the size of anappropriate prosthetic leaflet. A desired one of the contact members 82,86, 88 can be attached to the elongated member by any of a number ofmeans known in the art.

[0045]FIG. 11 illustrates an example of a cardiac prosthesis 100 thatcan be implanted according to the present method. For example, theprosthesis 100 can be of the type shown and described in U.S. patentapplication Ser. No. 10/215,800, filed on Aug. 4, 2002, to Gabbay, whichis hereby incorporated by reference.

[0046] The prosthesis 100 includes a generally arcuate base portion 102that can be closed or C-shaped. In accordance with an aspect of thepresent invention, a section of the base portion, indicated as a dottedportion 103, can be removable from the prosthesis 100 (e.g., by cutting)so that a surgeon can select the type of annulus desired—ring-like orC-shaped. The base portion 102 includes a support ring, which can beformed of a flexible, resilient, or generally rigid material. Thesupport ring can have an elastic property that returns the ring to itsoriginal shape when deflected from its original (or rest) condition. Thesupport ring, for example, can be a plastic-like material (e.g., apolymer, a resin, etc.) or a metal (e.g., stainless steel, a shapememory alloy, such as NITINOL), such as in the form of a wire. It willbe understood and appreciated that other types of generally rigid,elastic, and/or resilient materials also can be used in accordance withthe present invention. In addition, a suitable inelastically deformablematerial also could be used to form the support ring.

[0047] A buttress 104 extends generally axially from an outflow side 106of the base portion 102. Briefly stated, a proximal portion 108 of thebuttress 104 extends generally axially and radially inward from the baseportion 102. A distally extending portion 110 of the buttress 104extends from the proximal portion 108 and curves radially outwardlytherefrom for the remaining length of the buttress. The buttress 104 hasa radially inner surface 112 that provides a surface against which aleaflet (e.g., an anterior leaflet of a mitral valve) can coapt at valveclosure.

[0048] The prosthesis 100, including the buttress 104, can be selectedaccording to the dimensions and configuration of a contact member from asizing apparatus that has been determined to provide desired coaptation.Consequently, when the prosthesis 100 is implanted within a heart valve,a leaflet (or leaflets) can engage the buttress 104 to close the valveand provide substantially unidirectional flow of blood therethrough. Theleaflet (or leaflets) is able to coapt with the inner surface 112 of thebuttress 104, thereby inhibiting regurgitation of blood when theventricle contracts.

[0049] The prosthesis 100 can also include an outer sheath 114 of aflexible, biocompatible material covering the apparatus. The apparatus100 also can include an implantation flange 116 (or sewing ring) thatcircumscribes the base portion 102 of the apparatus. The implantationflange 116 extends radially outwardly from the base portion 102 forfacilitating implantation of the apparatus 100 at a heart valve. Each ofthe outer sheath 114 and the implantation flange 116 can be formed ofany suitable flexible, biocompatible material, such as a cloth-like orfabric (natural or synthetic) material or a biological material, such ascollagen or an animal tissue material. An acceptable animal tissuematerial is smooth animal pericardium (e.g., equine, bovine, porcine,etc.), such as a NO-REACT® tissue product, which is available fromShelhigh, Inc. of Union, N.J.

[0050] Implantation of a cardiac prosthesis can be accomplished byseveral means. For the type of prosthesis illustrated in FIG. 11, thesemeans will generally require open heart surgery. For example, the baseportion 102 can be sewn to the wall of the valve 54 at the implantationflange 116 to hold the prosthesis in place. The base portion 102 canalso include barbs or hooks (not shown) that extend radially from theexterior of the base potion, such as disclosed in the above incorporatedGabbay patent application. These barbs can be pressed into the wall ofthe valve to directly engage the muscle tissue of the valve.

[0051] The implantation of other types of prostheses can be lessinvasive. For example, a prosthesis can be designed to be reducible to asmaller cross-sectional dimension for placement via a catheter or a typeof implantation. The sizing tool and process used for these non-invasivetechniques can vary from those described above, in accordance withadditional aspects of the present invention.

[0052]FIG. 12 illustrates a part of a heart in which a prosthesis 130 isimplanted at a mitral valve 132. For the purpose of example, theimplanted prosthesis will be the type of prosthesis 100 illustrated inFIG. 11, but in which the removable section 103 of the annular base 102has been removed. It will be appreciated, however, that the presentinvention is not limited to use with this prosthesis. A number of othercardiac prostheses are available and suitable for use with the sizingapparatus of the present invention.

[0053] The valve 132 facilitates a unidirectional flow of blood from theleft atrium 134 into the left ventricle 136. The mitral valve 132includes an anterior leaflet 138 that extends from the valve opening andattaches to muscular tissue in the wall of the left ventricle by fibrouscordae tendinae 140. A posterior leaflet (not shown) extends from anopposing surface of the valve opening and coapts the anterior leaflet atvalve closure. In FIG. 12, the posterior leaflet has been substantiallyremoved from the heart, such as by excising it before implanting theprosthesis 130. It is to be understood and appreciated, however, thatthe posterior leaflet can remain intact, with a buttress 142 of theprosthesis 130 interposed between the posterior and anterior leaflets.

[0054] The buttress 142 extends from a base 144 of the prosthesis 130into the ventricle 136 at a position corresponding to the position ofthe posterior leaflet of the mitral valve 132. As mentioned above, thebuttress 142 extends into the ventricle 136 It is to be appreciated thatthe buttress 142 can be formed of a generally rigid material thatremains substantially stationary (e.g., static) during both the open andclosed positions of the valve. Alternatively, the buttress 142 can be asufficiently flexible- material to permit movement thereof commensuratewith the flow of blood from the atrium 136 into the ventricle 136through the valve 132.

[0055]FIG. 12 illustrates the anterior leaflet 138 engaging the buttress142 of the prosthesis 130, operating as a closed valve. In this way, thebuttress 142 of the prosthesis 130 simulates the function of theposterior leaflet at valve closure by providing a surface against whichthe anterior leaflet 138 coapts. Consequently, the buttress 142 and theanterior leaflet 138 cooperate to inhibit regurgitation of blood fromthe left ventricle 136 into the left atrium 136, such as duringventricular contraction.

[0056] The buttress 142, in conjunction with the anterior leaflet 138,facilitates and promotes unidirectional flow of blood when the valve isopen. In particular, when a prosthesis 130 of an appropriate size isimplanted, an opening or aperture extends through the implantedprosthesis 130 between the buttress 142 and the anterior leaflet 138.Advantageously, the movement of the anterior leaflet 138 relative to thebuttress 142, in response to the flow of blood during the contraction ofthe left atrium 136, provides a sufficient orifice to permit thesubstantially free flow of blood from the left atrium into the leftventricle 136. The buttress 142 also can be formed of a flexiblematerial that is able to move radially relative to the base portion 144to further facilitate blood flow.

[0057]FIG. 13 illustrates an apparatus 150 in accordance with anotheraspect of the invention. The apparatus 150 includes a contact member152. As is illustrated in FIG. 13, the contact member 152 can be capableof assuming multiple configurations having different associatedcross-sectional dimensions. The contact member has a curved surface 154with an associated shape and area varying with the configuration of thecontact member 152. In the example of FIG. 13, the cross-sectional widthdimension is shown to vary between W1 and W2, where W1>W2. In this way,a given apparatus can accommodate differently sized valves.Additionally, the positioning of the by contact member at the patient'sheart valve can be facilitated when the contact member is at a reducedcross-section. In at least one configuration of the contact member 152,the curved surface 154 is shaped to engage a leaflet within a heartvalve.

[0058] The contact member 152 can be made from a material having with anatural shape and a tendency to return to that natural shape in theabsence of a deforming force and the capacity to be deformed from thatnatural shape by pressure or some other means. By way of example, thecontact member can be formed from a shape memory alloy material, such asNitinol. Such an alloy can be formed into a particular shape and treatedto allow it to “remember” that form. At low temperatures, the materialremains pliant, but at higher temperatures, such as those within apatient's body, the material will attempt to revert to the rememberedform. The shape memory alloy can be coated with natural or syntheticmaterial, such as a soft plastic, rubber or biological material (e.g.,animal pericardium, dura matter, etc.).

[0059] For example, the natural shape of the material corresponds to theconfiguration of the contact member having the largest cross-sectionaldimension W1. It will be appreciated, however, that the apparatus may bedesigned such that the natural shape is the configuration with thesmallest cross-sectional dimension W2 or an intermediate cross-sectionaldimension, depending on the requirements of a given application.

[0060] The illustrated contact member 152 can be deformed into aconfiguration having a smaller cross-sectional dimension (e.g., lessthan W1) by one or more control members. In the illustrated embodiment,the control members include one or more elongated restraints 156 and158, such as sutures. It will be appreciated that the one or morecontrol members of the device may take a number of forms, and that theillustrated device is merely exemplary.

[0061] The restraints are connected at their distal ends to the lateraledges 160 and 162 of the contact member 152 to hold the contact memberin a configuration having a reduced cross-sectional dimension. Anelongated member 159 extends from the contact member 152 to a proximalend (not shown). One or more apertures (also not shown) extend throughthe elongated member 159 from its proximal end 162 to a point near thecontact surface 154 of the contact member 152. The restraints 156 and158 extend through one or more orifices 164 and 166 into the aperturewithin the elongated member 159 at a point near the contact surface 154.The restraints 156 and 158 extend through the aperture to a proximal end162 of the elongated member 160. At the proximal end, the restraints 156and 158 can be fastened by their proximal ends to a control device (notshown) to maintain a necessary tension within the restraints 156 and 158to deform the contact member 152.

[0062] The configuration of the contact member 152 can be controlled bythe control device at the proximal end of the elongated member 159. Thecontrol device is operative to increase or decrease the length of therestraints 156 and 158 between the proximal end 162 of the elongatedmember 159 and the lateral edges 160 and 162 of the contact member 152.As the portion of the restraints 156 and 158 between the proximal end162 and the lateral edges 160 and 162 of the contact member 152 isshortened, the restraints operate to pull the lateral edges closertogether, reducing the cross-sectional dimension of the contact member(e.g., to less than W1). When the tension on the restraints 156 and 158is loosened, such as to increase the length of the restraints betweenthe apertures 164 and 166 and the respective lateral edges 160 and 162,the lateral edges will move apart as the contact member 152 attemptingto return to its natural configuration (e.g., W1). The expanded sizethus will vary according to the length of the restraints between theapertures 164 and 166 and the respective lateral edges 160 and 162.

[0063] It will be appreciated that the control device can include any ofa number of devices useful in controlling the tension on the restraints156 and 158. For example, one or more wheels can gather a portion of therestraints 156 and 158 into a coil under manual or mechanical pressure.Alternatively, one or more restraining clips on the exterior of thedevice can be employed to enable the user to withdraw or release aportion of the restraints manually and clip the restraints into place ata desired length. Similar examples should be apparent to one skilled inthe art in light of the foregoing discussion.

[0064] Regardless of the specific control device used, markings orindicia can be provided on the device, for example, on the deviceexterior, to directly or indirectly measure the length of the restraints156 and 158 between the proximal end 162 and the lateral edges 160 and162 of the contact member 152. The apparatus 150 can be calibrated suchthat a particular length of one or more of the restraints 156 and 158will correspond to a cross-sectional dimension of the contact member152, allowing the cross-sectional dimension to be determined from themeasurement of the length of the one or more restraints.

[0065] An intended purpose of the apparatus 150 of FIG. 13 is its use ina minimally invasive sizing process to precede implantation of avalvuloplasty device, such as shown and described in theabove-incorporated Gabbay patent application. The illustrated contactmember 152 can be deformed to a configuration having a reducedcross-sectional dimension to facilitate placement of the device. Theapparatus 150 can be mounted to a catheter, an elongated handle, oranother positioning device for insertion into a heart valve. Anappropriate vision system can be included with the apparatus 150 toguide the placement of the apparatus 150 and determine if a particularconfiguration of the contact member provides effective coaptation withany viable leaflets in the valve.

[0066] Where the apparatus 150 is mounted to an elongated handle, a lowinvasive minithoracotomy can be used to gain access to the heart of thepatient and the apparatus 150 can be inserted through theminithoracotomy passage. The contact member 152 is first placed into aconfiguration having a minimal cross-sectional dimension. The surgeoncan then guide the apparatus 150 through the passage using anappropriate vision system to bring the contact member 152 into a desiredposition for engaging with any viable leaflets of the valve. Thecross-sectional dimension of the contact member can then be expanded tothe size where it engages with the viable leaflets and thecross-sectional dimension necessary to provide effective coaptation canbe recorded. The point where effective coaptation takes place can bedetermined by the surgeon using the vision system. The cross-sectionaldimension of the contact member 152 can then be reduced back to itsinitial, minimal configuration to facilitate withdrawal of the device.It will be appreciated that such a procedure can be implemented withlittle or no cardiopulmonary bypass.

[0067] Similarly, where the apparatus 150 is mounted to a catheter, itcan be inserted into the heart valve from a remote entry point withinthe body. When a catheter is used to position the apparatus 150, anelectromechanical mechanism can be used to adjust the length of therestraints 156 and 158 and accordingly, adjust the configuration of thecontact member 152, as the restraints 156 and 158 may not be in aposition to be manually adjusted. The cross-sectional dimension of thecontact member 152 can be reduced to facilitate passage through bloodvessels into the valve, and expanded to measure the size of a prostheticreplacement necessary to provide effective coaptation of any viableleaflets. The cross-sectional dimension of the contact member 152 canthen be reduced to allow the apparatus 150 to be removed.

[0068]FIG. 14 illustrates an apparatus 210 in accordance with anotheraspect of the invention. The apparatus 210 includes a contact member212. As is illustrated in FIG. 14, the contact member 212 is capable ofassuming a plurality (e.g., at least two) configurations, each having adifferent associated cross-sectional dimension. Two such dimensions aredepicted at W1 and W2, where W1>W2. The contact member 212 has a curvedsurface 214 with an associated shape and area varying with theconfiguration of the contact member 212. The size contact member 212thus is variable to accommodate differently sized heart valves.Additionally, the contact member can be provided in a sufficientlyreduce cross-sectional dimension to facilitate its positioning at apatient's heart valve by minimally invasive means according to an aspectof the present invention.

[0069] The contact member 212 (or at least the surface 214 thereof) isformed from a fluid impermeable membrane 241 defining an interiorchamber. The outer membrane 241 can be formed from rubber, flexibleplastic, or any other elastic, fluid-impermeable substance that issubstantially biocompatible. The interior chamber of the member 212 isconnected to a fluid source (not shown) that can be located near theproximal end of the elongated member 244 through a conduit 245 or otherfluid communicating member. The conduit 245, for example, can be formedas an aperture extending through the elongated member 244.

[0070] A control device (not shown) on the fluid source directs a fluidthrough the aperture 245 to the interior chamber. This mechanism can bea pump, a syringe, a bellows, or any similar device for encouraging theflow of fluid. The fluid itself may be air, water, saline, blood, or anyother biocompatible fluid. As the interior chamber fills with fluid, itinflates the outer membrane 241 causing the contact member 212 to assumea configuration having a cross-sectional dimension functionally relatedto the amount of fluid in the chamber of the member 212. Thecross-sectional dimension of the contact member 212 can be ascertainedaccording to the amount of fluid that is directed into the interiorchamber. The apparatus 210 can be calibrated such that a particularfluid level can be translated into an appropriate cross-sectionaldimension. A control device can include means for evacuating the fluidwithin the interior chamber, either back into the fluid source, or intothe heart valve.

[0071] An intended purpose of the apparatus 210 illustrated in FIG. 14is its use in a minimally invasive sizing process to precedeimplantation of a valvuloplasty device. In this process, the contactmember 212 begins with the outer membrane 241 deflated to provide areduced cross-sectional dimension that facilitates placement of thedevice. The apparatus 210 can be mounted to a catheter, an elongatedhandle, or another positioning device for insertion into a heart valve.The fluid source can connect to the contact member 212 through anaperture 246 in the elongated member 244. An appropriate vision systemcan be included with the device to guide the placement of the device anddetermine if a particular configuration of the contact member 212provides effective coaptation with any viable leaflets in the valve.

[0072] Where the apparatus 210 is mounted to an elongated handle, a lowinvasive minithoracotomy can be used to gain access to the heart of thepatient, such that the apparatus 210 can be inserted through theminithoracotomy passage. The contact member 212 is placed in a deflatedconfiguration having a minimal cross-sectional dimension to facilitatepositioning of the device. The surgeon can then guide the apparatus 210through the passage using an appropriate vision system to place thecontact member 212 at a desired position for engaging one or more viableleaflets of the valve. The cross-sectional dimension of the contactmember 212 can then be selectively expanded through inflation of theouter membrane 241 to the point where the viable leaflets can engage thesurface 214 to inhibit flow of fluid through the valve annulus (e.g.,simulating operation of competent heart valve). The cross-sectionaldimension necessary to provide effective coaptation can be recordedbased on the amount of fluid provided to the inner chamber, for example.The coaptation between the contact member and the valve leaflet (orleaflets) can be determined by the surgeon using the vision system. Thecross-sectional dimension of the contact member 212 can then be reducedback to its initial, minimal configuration to facilitate withdrawal ofthe device by evacuating the fluid within the device. It will beappreciated that such a procedure can be implemented with little or nocardiopulmonary bypass.

[0073] Similarly, the apparatus 210 can be mounted to a catheter forinsertion into the heart valve from a remote entry point of the body.When a catheter is used to position the apparatus 210, a separate tubecan be included to carry fluid to the interior chamber from the fluidsource to adjust the configuration of the contact member 212. Thecross-sectional dimension of the contact member 212 is placed in areduced form to facilitate passage through blood vessels into the valve.The inner chamber of the contact member 212 is then filled at leastpartially with fluid to expand the contact member 212 to determine asuitable size of a prosthetic device to provide effective coaptation ofany viable leaflets. The cross-sectional dimension of the contact member212 can then be reduced to allow the apparatus 210 to be removed byevacuating the fluid from the inner chamber.

[0074] In view of the foregoing, an apparatus according to the presentinvention provides a useful apparatus for determining the necessary sizefor a valvuloplasty device intended for implantation into a heart valve.A method for utilizing the apparatus for sizing a heart valve has beendescribed. Embodiments of the apparatus that are useful for a minimallyinvasive sizing procedure have been provided.

[0075] What has been described above are examples of the presentinvention. It is, of course, not possible to describe every conceivablecombination of components or methodologies for purposes of describingthe present invention, but one of ordinary skill in the art willrecognize that many further combinations and permutations of the presentinvention are possible. For example, while many of the illustratedexamples show the discuss the treatment of a bicuspid (mitral) valve, anapparatus in accordance with the present invention can also be useful insizing prosthetic devices for other types of heart valves (e.g., atricuspid valve or other bicuspid valves). Accordingly, the presentinvention is intended to embrace all such alterations, modifications andvariations that fall within the spirit and scope of the appended claims.Furthermore, to the extent that the term “includes” is used in eitherthe detailed description or the claims, such term is intended to beinclusive in a manner similar to the term “comprising.”

What is claimed is:
 1. A sizing apparatus for a prosthetic device,comprising: a contact member having a curved surface that is configuredto be engaged by at least one functioning leaflet of a heart valvewithin a patient when the contact member is positioned at the heartvalve; and an elongated member extending from the contact member andterminating in a proximal end.
 2. The sizing apparatus of claim 1,further comprising an aperture extending through the elongated memberfrom the proximal end and terminating in an opening end near the contactmember to facilitate flow of fluid therethrough.
 3. The sizing apparatusof claim 2, the aperture terminating near a surface of the contactmember opposite the curved surface.
 4. The sizing apparatus of claim 2,further comprising a fluid source operative to supply fluid into theaperture.
 5. The sizing apparatus of claim 4, the fluid source furthercomprising a syringe for providing fluid into the aperture.
 6. Thesizing apparatus of claim 4, further comprising a conduit interface thatextends from the proximal end of the elongated member and terminates ina proximal end portion thereof, the proximal end portion of the conduitinterface being adapted to connect to the fluid source.
 7. The sizingapparatus of claim 6, the conduit interface further comprising aflexible material.
 8. The sizing apparatus of claim 1, the contactmember having a first axis substantially parallel with the elongatedmember and a second axis substantially perpendicular with the elongatedmember, the contact member being curved along at least one of the firstand second axes.
 9. The sizing apparatus of claim 1, the contact memberbeing dimensioned and configured to approximate a radially inner surfaceof at least one leaflet at closure.
 10. The sizing apparatus of claim 1,the contact member being configured to provide a cross-sectionaldimension that is variable between a reduced cross-sectional dimensionto facilitate positioning thereof at the heart valve and an expandedcross-sectional dimension to facilitate determining the size of adesired cardiac prosthesis based on engagement between the contactmember and the at least one leaflet.
 11. The sizing apparatus of claim10, the contact member further comprising a fluid impermeable outermembrane having an inner chamber, the outer membrane defining thecross-sectional dimension of the contact member based on an amount offluid within the inner chamber.
 12. The sizing apparatus of claim 10,further comprising a control member operative to adjust thecross-sectional dimension of the contact member to a desired size. 13.The sizing apparatus of claim 10, further comprising a retainingmechanism operative to adjust the cross-sectional dimension of thecontact member to a desired size, the contact member beingself-expanding from the reduced cross-sectional dimension to theexpanded cross-sectional dimension.
 14. The sizing apparatus of claim13, the retaining mechanism further comprising at least one elongatedelements having distal ends connected to lateral edges of the contactmember and proximal ends that extend from the contact member, thecross-sectional dimension of the contact member, varying as a functionof the length of at least one of the connecting elements between theproximal end of the elongated member and the respective lateral edge ofthe contact member to which the at least one connecting element isconnected.
 15. The sizing apparatus of claim 10, the contact membercomprising a material having shape memory properties so that the contactmember is self-expanding from the reduced cross-sectional dimension tothe expanded cross-sectional dimension.
 16. An apparatus for determiningan appropriate size for a prosthetic device, comprising: means forcontacting at least one leaflet of a patient's heart valve, such thatthe amount of coaptation between the at least one leaflet and the meansfor contacting is indicative of sizing requirements for a cardiacprosthesis; and means to facilitate positioning the means for contactingto an appropriate position relative to the at least one leaflet of thepatient's heart valve, the means for positioning extending from themeans for contacting.
 17. An apparatus as set forth in claim 16,including means for urging the at least one viable leaflet toward themeans for contacting.
 18. A sizing apparatus for a prosthetic device,comprising: a contact member having a curved surface that is configuredto be engaged by at least one functioning leaflet of a heart valvewithin a patient when the contact member is positioned at the heartvalve; an elongated member extending from the contact member andterminating in a proximal end; and an aperture extending through theelongated member from the proximal end and terminating in an opening endproximal the contact member to facilitate flow of fluid therethrough.19. A method to facilitate selecting a cardiac prosthesis forimplantation at a patient's heart valve, the method comprising:positioning a contact member to an appropriate position relative to atleast one leaflet of the patient's heart valve; urging the at least oneleaflet of a patient's heart valve toward the contact member, thecontact member having a known cross-sectional dimension; and determiningsizing requirements for the cardiac prosthesis based on coaptationbetween the at least one leaflet and the contact member.
 20. The methodof claim 19, further comprising: selecting a cardiac prosthesis based onthe determined sizing requirements, the cardiac prosthesis comprising agenerally arcuate base and a buttress extending from the base; andimplanting the cardiac prosthesis at the patient's heart valve such thatthe at least one leaflet is moveable relative to the buttress to providesubstantially unidirectional flow of blood through the heart valve. 21.The method of claim 19, wherein the contact member is a first contactmember and the method further includes positioning a second contactmember having a different cross-sectional dimension than that of thefirst contact member in place of the first contact member.
 22. Themethod of claim 19, further comprising adjusting the cross-sectionaldimension of the contact member.
 23. The method of claim 22, wherein theadjusting of the cross-sectional dimension of the contact memberincludes one of supplying and removing fluid from within the contactmember.
 24. The method of claim 22, wherein the contact member isself-expanding from a reduced cross-sectional dimension to an expandedcross-sectional dimension, and the adjusting of the cross-sectionaldimension of the contact member includes adjusting a length of at leastone retaining mechanism that is operatively connected to the contactmember.